1. Field of the Invention
The present invention relates to a vacuum process apparatus, in which contamination of objects of process and production of particles can be prevented to improve the yield even in the case where the objects are cooled in a vacuum reserve chamber, and the vacuum reserve chamber can be used to preheat unprocessed objects and cool processed objects.
2. Information of the Related Art
In manufacturing processes for semiconductor devices, semiconductor wafers, as objects of process, are subjected to various processes, such as film formation, oxidation, doping, annealing, etching, etc. Some vacuum process apparatuses (Jpn. Pat. Appln. KOKAI Publication Nos. 3-19252, 4-133422, etc.) have been proposed in order to improve the throughput of the process processes, prevent production of particles, and save spaces.
In these vacuum process apparatuses, a vacuum reserve chamber, whose internal pressure can be restored to the level of the atmospheric pressure, is connected to vacuum process chambers in which wafers are subjected to predetermined processes. The wafers can be carried into or out of the vacuum process chambers through the vacuum reserve chamber.
In some vacuum process apparatuses, the vacuum reserve chamber is provided with a cooling table for cooling a processed high-temperature wafer. According to such vacuum process apparatuses, the processed wafer is set on the cooling table, and the vacuum reserve chamber is supplied with an inert gas so that its internal pressure is restored to the atmospheric pressure level as the wafer is cooled. Thus, the processed high-temperature wafer can be quickly brought to a chemically stable state such that it cannot easily react with the atmosphere, and therefore, the throughput can be improved.
When the wafers are cooled in the vacuum process apparatuses of this type, however, it is set on the cooling table in the vacuum reserve chamber in a manner such that its whole surface is in plane contact with the table. If the cooling table is formed of a metal, therefore, a metallic film or the like on the wafers and the metal of the table undergo a chemical reaction, so that the wafers may possibly be contaminated.
If the wafers are cooled rapidly, they may be somewhat warped and subjected to fine vibrations, in some cases. The fine vibrations cause the wafers to rub against the cooling table, so that particles are produced. These particles adhere to the wafers, possibly resulting in defectives and lowered yield.
In order to improve the throughput, moreover, there is a demand that the vacuum reserve chamber be used to preheat unprocessed objects of process and cool processed objects.